Breathing masks are often worn by workers in hazardous environments. One type of such a mask extends only over a user's nose and mouth, and contains a charcoal filter through which the air being breathed passes. The filter removes particles and toxic gases from the air. However, use of this type of breathing apparatus is typically prohibited by most fire departments as being inadequate, unreliable or unsafe in many environments where fire and smoke are present.
Instead, fire fighters are commonly approved to use safer self-contained breathing equipment when entering burning buildings. Such equipment includes a tank of compressed air and a pressure regulator to supply air at a constant pressure that can be tolerated by the fire fighter. A hose connects the air regulator to a full-face mask that is worn over the fire fighter's face. The mask includes an outlet for air exhaled by the fire fighter and a transparent visor. When worn by the user, the mask not only provides a sealed volume of breathable air over the user's face, but also protects the fire fighter's eyes from the smoke. Self-contained breathing apparatus with a full-face mask typically is the only type of smoke inhalation prevention equipment that is authorized by a fire department.
The tank of the fire fighter's breathing equipment has a finite supply of air. Although warning mechanisms are provided to alert the fire fighter when the supply of air is running low, there always is the possibility that the fire fighter will not be able to exit the burning structure before the exhaustion of the air supply. There is also a possibility that a fire fighter may become trapped within a burning structure, due to structure collapse, for example. The fire fighter may become lost in a large smoke-filled area, such as a shopping mall. The fire fighter could also be injured or incapacitated in someway and rendered immobile. In these instances, the fire fighter can run out of breathable air and be in imminent danger of death. As a consequence, it is desirable to provide an alternative breathing apparatus that protects against smoke inhalation for use in such imminent life-threatening emergencies.
Although a charcoal filter-type mouth filter could be provided to fire fighters for emergency back-up to authorized self-contained breathing apparatus, fire department officials are often concerned that such masks will be used routinely in the normal course of fire fighting and not reserved for imminent death situations, and therefore prohibit their use outright. Accordingly, it is desirable to provide a way of issuing back-up breathing devices to fire fighters in a manner which restricts their use to true emergency imminent death situations. It is also desirable to provide a mechanism by which fire fighters can quickly identify previous use and fire department officials can detect the unauthorized use of such emergency breathing devices.